Mass-Related Properties Of Transient Sprays

Hoffman, J. Mass-Related Properties Of Transient Sprays. University of Wisconsin-Madison, 1998.

The mass-related properties of transient fuel sprays intended for direct injection applications were investigated using transient patternation, numerical modeling, and light extinction droplet sizing.

The transient patternator was developed solely for the purpose of measuring axial liquid mass flux on a temporal and spatial basis. The device relies on a patternator commonly used in steady-state spray studies to measure liquid mass distributions within spray plumes. However, in this study a shutter consisting of a rotating disk was phased with a pulsing spray allowing various portions of the spray to be sampled. Derivations used to calculate the axial liquid mass flux using transient patternator data were provided. In addition to measuring axial liquid mass flux, the application of the conservation of mass allowed estimates of other properties such as axial velocities and liquid fuel to air ratios. The device and the derivations were applied to six injection systems for characterization.

The transient patternator was used to investigate six atomizer systems categorized into two types; air-assist and high-pressure. The data obtained from the transient patternator demonstrated large differences in the spatial and temporal position of mass-related properties among all atomizers.

Output from a computational fluid dynamics model designed to predict sprays from high-pressure atomizers was compared to data obtained with the transient patternator. The comparisons of axial liquid mass flux on a spatial and temporal basis demonstrated reasonable agreement between the two sources of data.

Lastly, work on a unique method referred to as dual light extinction for characterizing the line of sight droplet sizes and liquid mass within sprays was investigated. The method relies on commonly used light extinction physics for droplet sizing. However, the method in this study applies the light extinction method twice using two different detection angles simultaneously. The preliminary results look promising with the measurement of a particle reticle within 2% of the published Sauter mean diameter. In addition, a comparison between a dual light extinction and phase Doppler particle analyzer measurements of a steady state atomizer was within 0.4%. However, further investigation into this technique is necessary before it is fully proven.